Systems and methods for refrigerant leak management

ABSTRACT

A refrigerant leak management system includes a return inlet assembly and a purge exhaust outlet assembly. The system also includes a sensor configured to detect refrigerant proximate an air handling enclosure of a HVAC unit. The system further includes a controller configured to control the system to drive air from a conditioned interior space of a building into an external environment via the purge exhaust outlet assembly when the sensor detects the refrigerant proximate the air handling enclosure by: actuating the return inlet assembly to close the return inlet assembly, actuating the purge exhaust outlet assembly to open the purge exhaust outlet assembly, and activating a reversible supply fan of the HVAC unit in a reverse direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/871,685, filed Jan. 15, 2018, entitled “SYSTEMS AND METHODS FORREFRIGERANT LEAK MANAGEMENT,” which claims priority from and the benefitof U.S. Provisional Application No. 62/593,600, filed Dec. 1, 2017,entitled “SYSTEMS AND METHODS FOR REFRIGERANT LEAK MANAGEMENT,” whichare hereby incorporated by reference in their entirety for all purposes.

BACKGROUND

The present disclosure relates generally to heating, ventilating, andair conditioning (HVAC) systems, and more particularly to systems andmethods for refrigerant leak management in HVAC systems.

Residential, light commercial, commercial, and industrial HVAC systemsare used to control temperatures and air quality in residences andbuildings. Generally, the HVAC systems may circulate a refrigerantthrough a refrigeration circuit between an evaporator, where therefrigerant absorbs heat and a condenser where the refrigerant releasesheat. The refrigerant flowing within the refrigeration circuit isgenerally formulated to undergo phase changes within the normaloperating temperatures and pressures of the system so that quantities ofheat can be exchanged by virtue of the latent heat of vaporization ofthe refrigerant. As such, the refrigerant flowing within a HVAC systemtravels through multiple conduits and components of the refrigerationcircuit. Inasmuch as refrigerant leaks compromise system performance orresult in increased costs, it is accordingly desirable to providedetection and response systems and methods for the HVAC system toreliably detect and respond to any refrigerant leaks of the HVAC system.

SUMMARY

In one embodiment of the present disclosure, a refrigerant leakmanagement system for a heating, ventilation, and air conditioning(HVAC) unit configured to provide a conditioned interior space of abuilding includes a return inlet assembly and a purge exhaust outletassembly. The system also includes a sensor configured to detectrefrigerant proximate an air handling enclosure of the HVAC unit. Thesystem further includes a controller configured to control the system todrive air from the conditioned interior space of the building into anexternal environment via the purge exhaust outlet assembly when thesensor detects the refrigerant proximate the air handling enclosure by:actuating the return inlet assembly to close the return inlet assembly,actuating the purge exhaust outlet assembly to open the purge exhaustoutlet assembly, and activating a reversible supply fan of the HVAC unitin a reverse direction.

In another embodiment of the present disclosure, an air handling systemof a heating, ventilation, and air conditioning (HVAC) system configuredto manage airflow with respect to a conditioned interior space of abuilding includes a return inlet having a return inlet assembly and apurge exhaust outlet having a purge exhaust outlet assembly. The airhandling system includes a sensor configured to detect refrigerantproximate an air handling enclosure. The air handling system alsoincludes a reversible supply fan configured to draw air from theconditioned interior space of the building when operating in a reversedirection. Additionally, the air handling system includes a controllerconfigured to control the air handling system to purge the air into anexternal environment by operating the reversible supply fan in thereverse direction while the return inlet assembly is closed and thepurge exhaust outlet assembly is open, in response to the sensordetecting the refrigerant proximate the air handling enclosure.

In a further embodiment of the present disclosure, a method of operatinga heating, ventilation, and air conditioning (HVAC) system that providesa conditioned interior space of a building includes, in response todetecting refrigerant proximate an air handling enclosure of the HVACsystem via a sensor, activating a reversible supply fan of the HVACsystem in a reverse direction to draw a flow of air from the conditionedinterior space of the building. The method also includes closing areturn inlet assembly disposed at a return inlet of the air handlingenclosure to impede the flow of air from returning to the conditionedinterior space of the building. Additionally, the method includesopening a purge exhaust outlet assembly disposed at a purge exhaustoutlet of the air handling enclosure to guide the flow of air to enteran external environment.

Other features and advantages of the present application will beapparent from the following, more detailed description of theembodiments, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an embodiment of a commercial or industrialHVAC system, in accordance with present techniques;

FIG. 2 is an illustration of an embodiment of a packaged unit of theHVAC system, in accordance with present techniques;

FIG. 3 is an illustration of an embodiment of a split-type HVAC system,in accordance with present techniques;

FIG. 4 is a schematic diagram of an embodiment of a refrigeration systemof the HVAC system, in accordance with present techniques;

FIG. 5 is a schematic diagram of an embodiment a leak management systemof the HVAC system in active detection mode during an ON-cycle of theHVAC system, in accordance with present techniques;

FIG. 6 is a schematic diagram of the embodiment of the leak managementsystem of FIG. 5 in leak response mode during an OFF-cycle of the HVACsystem, in accordance with present techniques;

FIG. 7 is a schematic diagram of the embodiment of the leak managementsystem of FIG. 5 in leak response mode, in accordance with presenttechniques;

FIG. 8 is a front perspective view of an embodiment of a return inletassembly of the leak management system having locking mechanisms, inaccordance with present techniques;

FIG. 9 is a front perspective view of an embodiment of a return inletassembly of the leak management system having a motorized damper, inaccordance with present techniques; and

FIG. 10 is a flow diagram representing an embodiment of a process ofoperating the leak management system of FIG. 5, in accordance withpresent techniques.

DETAILED DESCRIPTION

As discussed above, a HVAC system generally includes a refrigerantflowing within a refrigeration circuit. However, in certain embodiments,the refrigerant may inadvertently leak from a flow path of therefrigeration circuit due to wear or degradation to components, orimperfect joints or connections within the refrigeration circuit, atsome point after installation. If undetected, leaking refrigerant maycompromise system performance or result in increased costs. As such,present techniques enable HVAC systems to reliably detect and managerefrigerant leaks.

With the foregoing in mind, present embodiments are directed to a leakmanagement system implemented in an air handling enclosure of a HVACsystem, such as an air handling unit of a residential HVAC system or anair handling portion of a packaged HVAC system, as discussed below. Morespecifically, the disclosed air handling enclosure includes a number ofairflow management assemblies positioned at various inlets and outletsof the air handling enclosure. The airflow management assembliesgenerally cooperate to enable the leak management system to effectivelydetect and mitigate refrigerant leaks within the enclosure. For example,the airflow management assemblies are capable of selectively directingan air flow within the air handling enclosure either to a conditionedinterior space of a building or to an external environment relative tothe conditioned interior space of the building.

Additionally, as discussed below, the leak management system may beoperated in various modes, including an active detection mode and a leakresponse mode. For example, the leak management system may operate in anactive detection mode to monitor refrigerant leaks both while the HVACsystem is operating in an ON-cycle that actively conditions the interiorspace, and while the HVAC system is operating in an OFF-cycle that doesnot actively condition the interior space. Additionally, in activedetection mode, a refrigerant gas concentration sensor measures aconcentration of leaking refrigerant within the air handling enclosure.When a sufficient refrigerant leak is detected, the leak managementsystem switches to leak response mode, in which one or more airflowmanagement assemblies are adjusted to fluidly couple the interior of theair handling enclosure to the external environment, and a reversiblesupply fan within the enclosure is operated in a reverse direction. Thereverse operation of the supply fan, in cooperation with the one or moreairflow management assemblies, purges leaked refrigerant from theinterior space of the air handling unit, from the building, and into theexternal environment. Indeed, the present embodiments of the leakmanagement system are capable of purging the air from the building, suchthat the leaked refrigerant is removed from the building. In thismanner, the disclosed techniques enable detection of leaked refrigerantwithin the air handling enclosure, and enable response via suitablecontrol actions to address the leaked refrigerant.

Turning now to the drawings, FIG. 1 illustrates a heating, ventilating,and air conditioning (HVAC) system for building environmental managementthat may employ one or more HVAC units. In the illustrated embodiment, abuilding 10 is air conditioned by a system that includes a HVAC unit 12.The building 10 may be a commercial structure or a residentialstructure. As shown, the HVAC unit 12 is disposed on the roof of thebuilding 10; however, the HVAC unit 12 may be located in other equipmentrooms or areas adjacent the building 10. The HVAC unit 12 may be asingle package unit containing other equipment, such as a blower,integrated air handler, and/or auxiliary heating unit. In otherembodiments, the HVAC unit 12 may be part of a split HVAC system, suchas the system shown in FIG. 3, which includes an outdoor HVAC unit 58and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigerationcycle to provide conditioned air to the building 10. Specifically, theHVAC unit 12 may include one or more heat exchangers across which an airflow is passed to condition the air flow before the air flow is suppliedto the building. In the illustrated embodiment, the HVAC unit 12 is arooftop unit (RTU) that conditions a supply air stream, such asenvironmental air and/or a return air flow from the building 10. Afterthe HVAC unit 12 conditions the air, the air is supplied to the building10 via ductwork 14 extending throughout the building 10 from the HVACunit 12. For example, the ductwork 14 may extend to various individualfloors or other sections of the building 10. In certain embodiments, theHVAC unit 12 may be a heat pump that provides both heating and coolingto the building with one refrigeration circuit configured to operate indifferent modes. In other embodiments, the HVAC unit 12 may include oneor more refrigeration circuits for cooling an air stream and a furnacefor heating the air stream.

A control device 16, one type of which may be a thermostat, may be usedto designate the temperature of the conditioned air. The control device16 also may be used to control the flow of air through the ductwork 14.For example, the control device 16 may be used to regulate operation ofone or more components of the HVAC unit 12 or other components, such asdampers and fans, within the building 10 that may control flow of airthrough and/or from the ductwork 14. In some embodiments, other devicesmay be included in the system, such as pressure and/or temperaturetransducers or switches that sense the temperatures and pressures of thesupply air, return air, and so forth. Moreover, the control device 16may include computer systems that are integrated with or separate fromother building control or monitoring systems, and even systems that areremote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. Inthe illustrated embodiment, the HVAC unit 12 is a single package unitthat may include one or more independent refrigeration circuits andcomponents that are tested, charged, wired, piped, and ready forinstallation. The HVAC unit 12 may provide a variety of heating and/orcooling functions, such as cooling only, heating only, cooling withelectric heat, cooling with dehumidification, cooling with gas heat, orcooling with a heat pump. As described above, the HVAC unit 12 maydirectly cool and/or heat an air stream provided to the building 10 tocondition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2, a cabinet 24 enclosesthe HVAC unit 12 and provides structural support and protection to theinternal components from environmental and other contaminants. In someembodiments, the cabinet 24 may be constructed of galvanized steel andinsulated with aluminum foil faced insulation. Rails 26 may be joined tothe bottom perimeter of the cabinet 24 and provide a foundation for theHVAC unit 12. In certain embodiments, the rails 26 may provide accessfor a forklift and/or overhead rigging to facilitate installation and/orremoval of the HVAC unit 12. In some embodiments, the rails 26 may fitinto “curbs” on the roof to enable the HVAC unit 12 to provide air tothe ductwork 14 from the bottom of the HVAC unit 12 while blockingmechanisms such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluidcommunication with one or more refrigeration circuits. Tubes within theheat exchangers 28 and 30 may circulate refrigerant through the heatexchangers 28 and 30. For example, the refrigerant may be R-410A. Thetubes may be of various types, such as multichannel tubes, conventionalcopper or aluminum tubing, and so forth. Together, the heat exchangers28 and 30 may implement a thermal cycle in which the refrigerantundergoes phase changes and/or temperature changes as it flows throughthe heat exchangers 28 and 30 to produce heated and/or cooled air. Forexample, the heat exchanger 28 may function as a condenser where heat isreleased from the refrigerant to ambient air, and the heat exchanger 30may function as an evaporator where the refrigerant absorbs heat to coolan air stream. In other embodiments, the HVAC unit 12 may operate in aheat pump mode where the roles of the heat exchangers 28 and 30 may bereversed. That is, the heat exchanger 28 may function as an evaporatorand the heat exchanger 30 may function as a condenser. In furtherembodiments, the HVAC unit 12 may include a furnace for heating the airstream that is supplied to the building 10. While the illustratedembodiment of FIG. 2 shows the HVAC unit 12 having two of the heatexchangers 28 and 30, in other embodiments, the HVAC unit 12 may includeone heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separatesthe heat exchanger 30 from the heat exchanger 28. Fans 32 draw air fromthe environment through the heat exchanger 28. Air may be heated and/orcooled as the air flows through the heat exchanger 28 before beingreleased back to the environment surrounding the rooftop unit 12. Ablower assembly 34, powered by a motor 36, draws air through the heatexchanger 30 to heat or cool the air. The heated or cooled air may bedirected to the building 10 by the ductwork 14, which may be connectedto the HVAC unit 12. Before flowing through the heat exchanger 30, theconditioned air flows through one or more filters 38 that may removeparticulates and contaminants from the air. In certain embodiments, thefilters 38 may be disposed on the air intake side of the heat exchanger30 to prevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing thethermal cycle. Compressors 42 increase the pressure and temperature ofthe refrigerant before the refrigerant enters the heat exchanger 28. Thecompressors 42 may be any suitable type of compressors, such as scrollcompressors, rotary compressors, screw compressors, or reciprocatingcompressors. In some embodiments, the compressors 42 may include a pairof hermetic direct drive compressors arranged in a dual stageconfiguration 44. However, in other embodiments, any number of thecompressors 42 may be provided to achieve various stages of heatingand/or cooling. As may be appreciated, additional equipment and devicesmay be included in the HVAC unit 12, such as a solid-core filter drier,a drain pan, a disconnect switch, an economizer, pressure switches,phase monitors, and humidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. Forexample, a high voltage power source may be connected to the terminalblock 46 to power the equipment. The operation of the HVAC unit 12 maybe governed or regulated by a control board 48. The control board 48 mayinclude control circuitry connected to a thermostat, sensors, andalarms. One or more of these components may be referred to hereinseparately or collectively as the control device 16. The controlcircuitry may be configured to control operation of the equipment,provide alarms, and monitor safety switches. Wiring 49 may connect thecontrol board 48 and the terminal block 46 to the equipment of the HVACunit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also inaccordance with present techniques. The residential heating and coolingsystem 50 may provide heated and cooled air to a residential structure,as well as provide outside air for ventilation and provide improvedindoor air quality (IAQ) through devices such as ultraviolet lights andair filters. In the illustrated embodiment, the residential heating andcooling system 50 is a split HVAC system. In general, a residence 52conditioned by a split HVAC system may include refrigerant conduits 54that operatively couple the indoor unit 56 to the outdoor unit 58. Theindoor unit 56 may be positioned in a utility room, an attic, abasement, and so forth. The outdoor unit 58 is typically situatedadjacent to a side of residence 52 and is covered by a shroud to protectthe system components and to prevent leaves and other debris orcontaminants from entering the unit. The refrigerant conduits 54transfer refrigerant between the indoor unit 56 and the outdoor unit 58,typically transferring primarily liquid refrigerant in one direction andprimarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, aheat exchanger 60 in the outdoor unit 58 serves as a condenser forre-condensing vaporized refrigerant flowing from the indoor unit 56 tothe outdoor unit 58 via one of the refrigerant conduits 54. In theseapplications, a heat exchanger 62 of the indoor unit functions as anevaporator. Specifically, the heat exchanger 62 receives liquidrefrigerant, which may be expanded by an expansion device, andevaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger60 using a fan 64 and expels the air above the outdoor unit 58. Whenoperating as an air conditioner, the air is heated by the heat exchanger60 within the outdoor unit 58 and exits the unit at a temperature higherthan it entered. The indoor unit 56 includes a blower or fan 66 thatdirects air through or across the indoor heat exchanger 62, where theair is cooled when the system is operating in air conditioning mode.Thereafter, the air is passed through ductwork 68 that directs the airto the residence 52. The overall system operates to maintain a desiredtemperature as set by a system controller. When the temperature sensedinside the residence 52 is higher than the set point on the thermostat,or the set point plus a small amount, the residential heating andcooling system 50 may become operative to refrigerate additional air forcirculation through the residence 52. When the temperature reaches theset point, or the set point minus a small amount, the residentialheating and cooling system 50 may stop the refrigeration cycletemporarily.

The residential heating and cooling system 50 may also operate as a heatpump. When operating as a heat pump, the roles of heat exchangers 60 and62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58will serve as an evaporator to evaporate refrigerant and thereby coolair entering the outdoor unit 58 as the air passes over outdoor the heatexchanger 60. The indoor heat exchanger 62 will receive a stream of airblown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70.For example, the indoor unit 56 may include the furnace system 70 whenthe residential heating and cooling system 50 is not configured tooperate as a heat pump. The furnace system 70 may include a burnerassembly and heat exchanger, among other components, inside the indoorunit 56. Fuel is provided to the burner assembly of the furnace 70 whereit is mixed with air and combusted to form combustion products. Thecombustion products may pass through tubes or piping in a heat exchangerthat is separate from heat exchanger 62, such that air directed by theblower 66 passes over the tubes or pipes and extracts heat from thecombustion products. The heated air may then be routed from the furnacesystem 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can beused in any of the systems described above. The vapor compression system72 may circulate a refrigerant through a circuit starting with acompressor 74. The circuit may also include a condenser 76, an expansionvalve(s) or device(s) 78, and an evaporator 80. The vapor compressionsystem 72 may further include a control panel 82 that has an analog todigital (A/D) converter 84, a microprocessor 86, a non-volatile memory88, and/or an interface board 90. The control panel 82 and itscomponents may function to regulate operation of the vapor compressionsystem 72 based on feedback from an operator, from sensors of the vaporcompression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or moreof a variable speed drive (VSDs) 92, a motor 94, the compressor 74, thecondenser 76, the expansion valve or device 78, and/or the evaporator80. The motor 94 may drive the compressor 74 and may be powered by thevariable speed drive (VSD) 92. The VSD 92 receives alternating current(AC) power having a particular fixed line voltage and fixed linefrequency from an AC power source, and provides power having a variablevoltage and frequency to the motor 94. In other embodiments, the motor94 may be powered directly from an AC or direct current (DC) powersource. The motor 94 may include any type of electric motor that can bepowered by a VSD or directly from an AC or DC power source, such as aswitched reluctance motor, an induction motor, an electronicallycommutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vaporto the condenser 76 through a discharge passage. In some embodiments,the compressor 74 may be a centrifugal compressor. The refrigerant vapordelivered by the compressor 74 to the condenser 76 may transfer heat toa fluid passing across the condenser 76, such as ambient orenvironmental air 96. The refrigerant vapor may condense to arefrigerant liquid in the condenser 76 as a result of thermal heattransfer with the environmental air 96. The liquid refrigerant from thecondenser 76 may flow through the expansion device 78 to the evaporator80.

The liquid refrigerant delivered to the evaporator 80 may absorb heatfrom another air stream, such as a supply air stream 98 provided to thebuilding 10 or the residence 52. For example, the supply air stream 98may include ambient or environmental air, return air from a building, ora combination of the two. The liquid refrigerant in the evaporator 80may undergo a phase change from the liquid refrigerant to a refrigerantvapor. In this manner, the evaporator 38 may reduce the temperature ofthe supply air stream 98 via thermal heat transfer with the refrigerant.Thereafter, the vapor refrigerant exits the evaporator 80 and returns tothe compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further includea reheat coil in addition to the evaporator 80. For example, the reheatcoil may be positioned downstream of the evaporator relative to thesupply air stream 98 and may reheat the supply air stream 98 when thesupply air stream 98 is overcooled to remove humidity from the supplyair stream 98 before the supply air stream 98 is directed to thebuilding 10 or the residence 52.

It should be appreciated that any of the features described herein maybe incorporated with the HVAC unit 12, the residential heating andcooling system 50, or other HVAC systems. Additionally, while thefeatures disclosed herein are described in the context of embodimentsthat directly heat and cool a supply air stream provided to a buildingor other load, embodiments of the present disclosure may be applicableto other HVAC systems as well. For example, the features describedherein may be applied to mechanical cooling systems, free coolingsystems, chiller systems, or other heat pump or refrigerationapplications.

FIG. 5 is a schematic diagram of a HVAC system 100 having a leakmanagement system 102 for detecting and controlling a concentration ofleaked refrigerant within the HVAC system 100 and/or a building, such asthe building 10 discussed above. As shown, the HVAC system 100 includesa refrigeration circuit 104 having an evaporator coil 106 fluidlycoupled with a compressor 108, a condenser 110, and an expansion device112. A refrigerant 116 flows between HVAC components of therefrigeration circuit 104, undergoing phase changes that enable the HVACsystem 100 to condition an interior space of the building 10. Therefrigerant 116 may be any suitable refrigerant, such as R32, R1234ze,R1234yf, R-454A, R-454C, R-455A, R-447A, R-452B, R-454B, and the like.Each of the evaporator coil 106, the compressor 108, the condenser 110,and the expansion device 112 may correspond with any corresponding HVACdevices discussed above with reference to FIGS. 1-4. Moreover, theevaporator coil 106, the compressor 108, the condenser 110, and theexpansion device 112 may be part of any suitable residentialrefrigeration system, commercial refrigeration system, splitrefrigeration system, and/or single unit refrigeration system. As willbe discussed in more detail below, the leak management system 102 iscapable of detecting a leak of the refrigerant 116 from therefrigeration circuit 104, and performing suitable control actions tomitigate the leak of the refrigerant 116.

Additionally, the illustrated embodiment of the HVAC system 100 in FIG.5 includes the evaporator coil 106 disposed within an enclosure 120 ofthe HVAC system 100. The enclosure 120 is generally an air handlingenclosure or air handler of the HVAC system 100. Additionally, theenclosure 120 is a structurally strong and/or rigid container or boxhaving walls that fluidly isolate an interior 122 of the enclosure 120from an exterior 124 of the enclosure 120. In some embodiments, thefluid separation between the interior 122 and the exterior 124 may beair-tight, though in other embodiments, airflow may occur across seams,joints, gaskets, or other features of the enclosure 120. Moreover, incertain embodiments, the enclosure 120 is disposed in an attic, in asupply or utility room, on a roof or wall of a building, or in anothersuitable location to enable conditioning of the interior space of thebuilding 10.

The disclosed enclosure 120 includes various openings that serve asinlets or outlets for airflow therethrough. For example, as illustratedin FIG. 5, the enclosure 120 includes a return inlet 130 for receivingair from the interior space of the building 10, a supply outlet 132 fordirecting a conditioned airflow 156 to the interior space of thebuilding 10, and a purge exhaust outlet 134 for directing air out of theenclosure 120. Additionally, a plurality of ducts 138 to direct the airto and from the enclosure 120 include a return inlet duct 138A coupledto the return inlet 130, a supply outlet duct 138B coupled to the supplyoutlet 132, and a purge exhaust outlet duct 138C coupled to the purgeexhaust outlet 134. In general, the ducts 138 are passageways thatfluidly connect the interior 122 of the enclosure to various locationsinside or outside of the building 10. Further, in certain embodiments,the purge exhaust outlet duct 138C, which corresponds to the purgeexhaust outlet 134, includes a proximal portion 140 fluidly coupled tothe purge exhaust outlet 134, and a distal portion 142 fluidly coupledto a fresh air source, such as an environment that is external to thebuilding 10 and/or the enclosure 120, or an environment within thebuilding 10 that is unoccupied. For example, if the enclosure 120 isdisposed in an attic or utility room of the building, the purge exhaustoutlet 134 may be fluidly couple, via the purge exhaust outlet duct138C, the interior 122 of the enclosure 120 to the outside environment.Additionally, in some embodiments, the purge exhaust outlet duct 138Cmay be excluded, such that the purge exhaust outlet 136 is an openinginto the attic, supply room, or outside environment.

As illustrated in the embodiment of FIG. 5, an unconditioned airflow144, including air from the interior space of the building 10, isdirected into the enclosure 120 along the return inlet duct 138A and thereturn inlet 130. Additionally, in some embodiments, the unconditionedairflow 144 may include outside air that is mixed with the air from theinterior space of the building 10. In the embodiment illustrated in FIG.5, the unconditioned airflow 144 travels through multiple componentswithin the enclosure 120. For example, the unconditioned airflow 144travels through a filter 150 that removes particulates, dust, bacteria,or other undesired matter within the unconditioned airflow 144. Incertain embodiments, the unconditioned airflow 144 also travels througha heating coil or other suitable components that heat the unconditionedairflow 144 to remove humidity or otherwise condition the unconditionedairflow 144. Further, when actuated, a reversible supply fan 154disposed within the enclosure 120 receives the unconditioned airflow144, and moves the unconditioned airflow 144 at an increased speedand/or flowrate through the enclosure 120. When in an ON-cycle, thesupply fan 154 operates in the forward direction, such that the supplyfan 154 directs the unconditioned airflow 144 to the evaporator coil106, which cools the unconditioned airflow 144 and/or removes dissolvedmoisture, such as humidity, from the unconditioned airflow 144 byenabling heat transfer between the refrigerant 116 and the unconditionedairflow 144. The unconditioned airflow 144 is, therefore, conditionedand transformed into the conditioned airflow 156 that travels out of thesupply outlet 132 and to the interior space of the building 10 havingthe HVAC system 100.

In general, the supply fan 154 of the leak management system 102 iscapable of being run in reverse, such as by reversing polarity ofelectrical power provided to the supply fan 154. That is, the supply fan154 is powered by a reversible motor and, thus, can operate in forwardmodes and reverse modes, as compared to a unidirectional motor thatenables a non-reversible supply fan to only operate in a forward mode.In certain embodiments, the supply fan 154 is powered by a variablespeed drive (VSD), such as the VSD 92 discussed above, for variablecontrol of fan speeds in both the forward and reverse modes.

In the embodiment illustrated in FIG. 5, the leak management system 102includes a controller 170 to control operations therein. Additionally,for the illustrated embodiment, the controller 170 is the HVACcontroller that governs operation of the entire HVAC system 100,including the compressor 108, supply fan 154 and more, in addition tothe leak management system 102. The controller 170 may include adistributed control system (DCS) or any computer-based workstation. Forexample, the controller 170 can be any device employing a generalpurpose or an application-specific processor 174, both of which maygenerally include memory 172 or suitable memory circuitry for storinginstructions and/or data. However, in certain embodiments, thecontroller 170 may be a separate controller for controlling the leakmanagement system 102 that is communicatively coupled to exchange dataand/or instructions with a HVAC controller or another suitable mastercontroller.

The processor 174 illustrated in FIG. 5 may include one or moreprocessing devices, and the memory 172 may include one or more tangible,non-transitory, machine-readable media collectively storing instructionsexecutable by the processor 174 to control the leak management system102 and/or the HVAC system 100. The processor 174 of the controller 170provides control signals to operate the leak management system 102 andthe HVAC system 100 to perform the control actions disclosed herein.More specifically, as discussed below, the controller 170 receives inputsignals from various components of the HVAC system 100 and outputscontrol signals to control and communicate with various components inthe HVAC system 100. The controller 170 may provide suitable controlsignals to control the flowrates, motor speeds, and valve positions,among other parameters, of the HVAC system 100.

Although the controller 170 has been described as having the processor174 and the memory 172, it should be noted that the controller 170 mayinclude or be communicatively coupled to a number of other computersystem components to enable the controller 170 to control the operationsof the HVAC system 100 and the related components. For example, thecontroller 170 may include a communication component that enables thecontroller 170 to communicate with other computing systems andelectronic devices, such as alarm systems. The controller 170 may alsoinclude an input/output component that enables the controller 170 tointerface with users via a graphical user interface or the like. Inaddition, the communication between the controller 170 and othercomponents of the HVAC system 100 may be via a wireless connection, suchas a connection through Bluetooth® Low Energy, ZigBee®, WiFi®, or may bea wired connection, such as a connection through Ethernet. In someembodiments, the controller 170 may include a laptop, a smartphone, atablet, a personal computer, a human-machine interface, or the like.Additionally, the embodiments disclosed herein may be at least partiallyembodied using hardware implementations. For example, logic elements ofthe controller 170 may include a field-programmable gate array (FPGA),or other specific circuitry.

Moreover, the leak management system 102 includes several components todetect and manage leaks of the refrigerant 116 into the enclosure 120.As shown in the embodiment in FIG. 5, a plurality of airflow managementassemblies 158 is disposed within the enclosure 120 to control the flowof air into or from the enclosure 120. As used herein, controlling arespective flow of air is intended to cover blocking or allowing therespective flow of air into our out of respective spaces. Thus, theplurality of airflow management assemblies 158 includes a return inletassembly 160 and a purge exhaust outlet assembly 164 respectivelydisposed within the return inlet 130 and the purge exhaust outlet 134.Additionally, each airflow management assembly 158 receives controlsignals from the controller 170 that instruct each airflow managementassembly 158 to move between an open position that enables air to flowthrough the respective inlet or outlet having the airflow managementassembly 158, and a closed position that blocks air from flowing throughthe respective inlet or outlet having the airflow management assembly158. Thus, the airflow management assemblies 158 are capable of beingcontrolled to selectively direct air to flow into the enclosure 120, orto enable the air to flow out of the enclosure 120 in a specific manner,as discussed in more detail below. Additionally, closed or openpositions of the airflow management assemblies 158 are intended torespectively cover substantially or partially closed positions andsubstantially or partially open positions.

In some embodiments, as shown in the leak management system 102 of FIG.5, each airflow management assembly 158 includes a respective damper 180that pivots circumferentially around a pivot member 182. In someembodiments, the pivot member 182 includes pins that extend along anaxis 184 into or out of the page into recesses or openings in theenclosure 120 to provide an axis of rotation of the damper 180. Further,in some embodiments, the airflow management assemblies 158 may includecomputer-responsive or active elements, such as locking mechanisms ormotorized components that operate in response to control signalsprovided from the controller 170, as discussed in more detail withreference to FIGS. 8 and 9 below. As such, for the illustratedembodiment, in response to pressure or airflows pressing against anunlocked damper 180, the unlocked damper 180 swings open to enable theairflows to pass therethrough.

Additional contemplated embodiments include airflow managementassemblies 158 having one or more passive components that operatewithout instruction from the controller 170. In such embodiments, one ormore of the dampers 180 of the airflow management assemblies 158 may bebarometric dampers capable of being pushed open when the unconditionedairflow 144 passes or traverses through the dampers 180, and that remainclosed when the unconditioned airflow 144 is not present, such as whenthe supply fan 154 is not active. Additionally, in some embodiments, oneor more of the dampers 180 may be self-closing and/or reversespring-loaded to facilitate the closing of the dampers 180. Moreover, infurther embodiments, a portion of the airflow management assemblies 158are actively controlled, computer-responsive elements, and anotherportion of the airflow management assemblies 158 are passively orindirectly controlled by the controller 170 via control of the supplyfan 154. For example, the return inlet assembly 160 may be activelycontrolled in some embodiments, while the purge exhaust outlet assembly164 is passively controlled. Additionally, in some embodiments, anairflow management assembly 158 is also included in the supply outlet132, such that the enclosure 120 may be fluidly sealed or isolatedduring OFF-cycle of the HVAC system 100, such as to concentrate anyleaking refrigerant in the enclosure 120 for detection.

The leak management system 102 may operate in active detection modeduring both the ON-cycle and the OFF-cycle of the HVAC system 100. Todetect leaks in active detection mode, the embodiment of the leakmanagement system 102 illustrated in FIG. 5 includes a plurality ofconcentration sensors 190. For example, as shown, a first concentrationsensor 190A is disposed within the enclosure 120 near or proximate thesupply fan 154, a second concentration sensor 190B is disposed withinthe enclosure 120 near or proximate the evaporator coil 106, and a thirdconcentration sensor 190C is disposed within the supply outlet duct138B. Additionally, as used herein, a respective concentration sensor190 is “proximate” or near another element when the respectiveconcentration sensor 190 is capable of measuring a concentration of therefrigerant 116 within sensing range of the evaporator coil 106,disposed within a threshold distance of the element and/or adjacent tothe element.

The concentration sensors 190 are communicatively coupled to thecontroller 170 to transmit sensor signals to the controller 170indicative of a concentration of the refrigerant 116 that has leakedinto the interior 122 of the enclosure 120 or within the supply outletduct 138B. Additional embodiments include additional concentrationsensors 190 positioned within the interior space of the building 10,such as within ductwork 14 illustrated in FIG. 1, to detect theconcentration of the refrigerant 116 within the interior space of thebuilding 10 as well. However, as discussed herein, the concentrationsensors 190 are generally disposed proximate the enclosure 120 to enablethe concentration sensors 190 to monitor potential leaks of therefrigerant 116 from the evaporator coil 106 or other components of therefrigeration circuit 104. As used herein, “proximate” with respect tocomponents of the HVAC system 100 indicates being inside of, adjacentto, proximate to, and/or within inches or feet of the components of theHVAC system 100, while “proximate” with respect to the HVAC system 100indicates being proximate or within the HVAC system 100.

As illustrated in the embodiment of FIG. 5, the first concentrationsensor 190A is disposed upstream of the supply fan 154 relative to aforward airflow direction 198 through the enclosure 120 whenconditioning air. As will be discussed with reference to FIG. 7 below,the first concentration sensor 190A may thus enable detection of theconcentration of the refrigerant 116 traversing the supply fan 154 whenthe supply fan 154 is operating in reverse. Additionally, asillustrated, the second concentration sensor 190B is downstream of theevaporator coil 106 relative to the forward airflow direction 198through the enclosure 120 to enable detection of the concentration ofthe refrigerant 116 during forward operation of the supply fan 154. Inother embodiments, the second concentration sensor 190B is disposedupstream of the evaporator coil 106 or in another location suitable forsensing the concentration of the refrigerant 116, such as below theevaporator coil 106. When disposed proximate the evaporator coil 106, itis presently recognized that the second concentration sensor 190B iscloser to a greater quantity of braze joints, solder joints, or otherpotential leaks of the refrigerant 116 from the evaporator coil 106,thus enhancing detection of the refrigerant leaks. Additionally,although three concentration sensors 190 are discussed herein, anysuitable number of concentration sensors 190 may be included proximatethe evaporator coil 106, the enclosure 120, the ducts 138, and/or theinterior space of the building 10. For example, in certain embodimentshaving multiple concentration sensors 190 proximate the HVAC system 100,the controller 170 is capable of triangulating, locating, or pinpointinga position of a refrigerant leak via the signals received from themultiple concentration sensors 190.

The concentration sensors 190 may be any suitable type of concentrationsensors, including electrochemical gas detectors, catalytic beadsensors, photoionization detectors, infrared point sensors, infraredimaging sensors, semiconductor sensors, ultrasonic gas detectors,holographic gas sensors, or any other suitable concentration sensorcapable of detecting a concentration of the refrigerant 116. Moreover,although discussed herein as having concentration sensors 190, the leakmanagement system 102 may, additionally or alternatively, include othersensors suitable for detecting a presence of the refrigerant 116 withinthe enclosure 120, such as temperature sensors, pressure sensors,acoustic sensors, flowrate sensors, etc. Accordingly, with the aboveunderstanding of the components of the leak management system 102, theexample embodiment of the leak management system 102 operating in activedetection mode during ON-cycle of the HVAC system 100 (FIG. 5), inactive detection mode during OFF-cycle of the HVAC system 100 (FIG. 6),and in leak response mode (FIG. 7) discussed below may be more readilyunderstood.

In general, the HVAC system 100 is capable of switching between anON-cycle in which the compressor 108 draws or drives the refrigerant 116within the refrigeration circuit 104 to condition the interior space,and an OFF-cycle in which the compressor 108 does not motivate therefrigerant 116 through the refrigeration circuit 104. Additionally, theleak management system 102 is capable of switching between variousoperating modes, such as an active detection mode and leak responsemode, to enable detection and mitigation of refrigerant leaks. Theembodiment of the HVAC system 100 illustrated in FIG. 5 is in anON-cycle that conditions the interior space of the building. For theillustrated embodiment, when the HVAC system 100 is in the ON-cycle, theleak management system 102 is in the active detection mode, and thus thecontroller 170 instructs the return inlet assembly 160 to enable theunconditioned airflow 144 to flow therethrough. The controller 170 alsoinstructs the purge exhaust outlet assembly 164 to close or remainclosed, such that the unconditioned airflow 144 is not capable ofpassing therethrough. Additionally, the controller 170 activates thecompressor 108, which cycles the refrigerant 116 to condition theunconditioned airflow 144. Additionally, the HVAC system 100 drives thesupply fan 154 in forward operation, which provides the unconditionedairflow 144 from the interior space of the building 10, within theenclosure 120, across the concentration sensors 190, and back to theinterior space of the building 10.

Thus, in active detection mode, the controller 170 of the illustratedleak management system 102 measures the refrigerant concentration byreceiving the signals from the concentration sensors 190 indicative ofthe concentration of the refrigerant 116 that may have leaked from therefrigeration circuit 104 and into the enclosure 120 or the ducts 138.Then, based on the signals, the controller 170 determines theconcentration of the refrigerant 116. Additionally, in some embodiments,the concentration sensors 190 provide binary signals indicative ofwhether a threshold amount of the refrigerant 116 is detected or is notdetected. For example, during operation of the HVAC system 100, a leakof the refrigerant 116 may not be present. Thus, if no leak of therefrigerant 116 is present, the controller 170 may determine that theconcentration of the refrigerant 116 is below a lower detection limit ofthe concentration sensors 190. However, when refrigerant 116 leaks fromthe evaporator coil 106 and is sensed by the concentration sensors 190,the controller 170 receives the signals and determines a non-zeroconcentration of the refrigerant 116 within the enclosure 120 or theducts 138.

Additionally, the controller 170 compares the concentration of therefrigerant 116 to a predefined concentration threshold. The predefinedconcentration threshold may be a user-set, technician-set, ordistributor-set value that is stored within the memory 172 of controller170, either before or after the controller 170 is placed into operationwithin the HVAC system 100. In some embodiments, the predefinedconcentration threshold may be set as the lower detection limit of theconcentration sensors 190. In response to determining that theconcentration of the refrigerant 116 is less than the predefinedconcentration threshold, the controller 170 continues to operate theleak management system 102 in the active detection mode to continue todetermine the concentration of the refrigerant 116. In some embodiments,the controller 170 and the concentration sensors 190 may also wait apredefined time threshold before determining the concentration of therefrigerant 116 again, thus enhancing a useable life of theconcentration sensors 190 and/or reducing usage of computing power ofthe controller 170. In certain embodiments, the predefined timethreshold is set as 1 minute, 5 minutes, 10 minutes, 60 minutes, ormore.

In response to determining that the concentration of the refrigerant 116is greater than the predefined concentration threshold, the controller170 determines that a leak of the refrigerant 116 is present within theenclosure 120 or the ducts. Thus, to perform suitable control actionsfor managing the detected leak of the refrigerant 116, the leakmanagement system 102 enters the leak response mode, in which the supplyfan 154 is operated in reverse to purge air out of the interior space ofthe building 10 and out of the purge exhaust outlet 134, as discussed indetail with reference to FIG. 7 below.

FIG. 6 is a schematic diagram of the leak management system 102 of FIG.5, in which the HVAC system 100 is in OFF-cycle. The illustratedembodiment of the leak management system 102 is in the active detectionmode for detecting a concentration of the refrigerant 116 that may leakfrom the refrigeration circuit 104 under certain conditions. Asdiscussed previously, the HVAC system 100 is in the OFF-cycle wheneverthe compressor 108 is not active. Further, when the HVAC system 100 isin the OFF-cycle, and when a fan-only or ventilation function of theHVAC system 100 is not requested, the controller 170 may instruct thesupply fan 154 to deactivate. Thus, without the force of the supply fan154 to draw the unconditioned airflow 144 through the return inletassembly 160 or to push an airflow through the purge exhaust outletassembly 164, the illustrated airflow management assemblies 158 remainin the closed position. In this manner, a leak of the refrigerant 116within the enclosure 120 or within the ducts 138 may be confined withinthe HVAC system 100. Accordingly, the controller 170 operates the leakmanagement system 102 in active detection mode to monitor aconcentration of the refrigerant 116 during OFF-cycles of the HVACsystem 100, in addition to the ON-cycle discussed above. However, inother embodiments of the airflow management assemblies 158 withoutcomputer-responsive components, one or more of the dampers 180 may beself-closing dampers that automatically rotate via gravity, springs,etc., back to the closed position when an airflow is not present.

Further, in certain embodiments, the controller 170 may receive thesignals from the concentration sensors 190 indicative of the respectiveconcentration of the refrigerant 116 proximate each concentration sensor190, and then determine a location of the refrigerant leak based on therelative concentrations proximate each concentration sensor 190. Forexample, in certain conditions, the controller 170 determines thatbecause the first concentration sensor 190A senses a greaterconcentration of the refrigerant 116 than the second concentrationsensor 190B, the location of the leak of the refrigerant 116 is closerto the first concentration sensor 190A than the second concentrationsensor 190B. By determining the location of the leak during theOFF-cycle of the HVAC system, the controller 170 may provide theinformation to users for repairing the leak for effectively. Then, afterdetermining that the concentration of the refrigerant 116 is above thepredefined concentration threshold, the controller 170 operates the leakmanagement system 102 in the leak response mode.

For example, FIG. 7 is a schematic diagram of the embodiment of the HVACsystem 100 with the leak management system 102 in leak response mode. Inleak response mode, the controller 170 provides control signals orrequests to a master controller modifying operation of the HVAC system100. In some embodiments, the control signals prompt the HVAC system 100to provide alerts and/or mitigating actions for a detected refrigerantleak identified via the concentration of the refrigerant 116 exceedingthe predefined concentration threshold. For example, the controller 170may transmit the control signal to instruct a device, such as athermostat, a user device, and/or a service technician workstation, togenerate an alert indicative of the detected refrigerant leak. In someembodiments, the alert also includes instructions to deactivateactivation sources and/or to instruct users to respond appropriately.Once informed of the detected refrigerant leak, users may perform manualcontrol actions, such as shutting off the HVAC system 100 or repairing aportion of the evaporator coil 106, in response to the detectedrefrigerant leak.

Additionally or alternatively, the control signals from the controller170 may modify operation of the HVAC system 100 to mitigate the detectedrefrigerant leak. For example, in certain conditions, the controller 170provides control signals that instruct the airflow management assemblies158 of the leak management system 102 to move to a leak responseorientation or closed configuration corresponding to the leak responsemode, and then operate the supply fan 154 in reverse to purge air fromthe interior space of the building 10, as illustrated in FIG. 7. Moreparticularly, as shown in the embodiment of the leak management system102 in the leak response orientation, the return inlet 130 is closed viathe return inlet assembly 160, and the purge exhaust outlet 134 is openrelative to the purge exhaust outlet assembly 164. To realize thesepositions, for the illustrated embodiment, the controller 170 instructslocking mechanisms of the return inlet assembly 160 to actuate to alocked position, thus blocking the corresponding damper 180 fromrotating to an open position in response to an airflow when the supplyfan 154 is activated in reverse to purge or vent the building 10.Additionally, when in the leak response orientation corresponding to theleak response mode, the controller instructs the locking mechanisms ofthe purge exhaust outlet assembly 164 to actuate to an unlocked positionthat enables the corresponding damper 180 to rotate in response to theairflow from the supply fan 154.

Further, as illustrated in FIG. 7, the controller 170 activates thesupply fan 154 in reverse by reversing a polarity of a power sourcesupplied to the supply fan 154 to draw a purge airflow 200 from theinterior space of the building 10, into the supply outlet 132 of theenclosure 120, and out of the open purge exhaust outlet 134. This leakresponse orientation of the airflow management assemblies 158 fluidlycouples the interior 122 of the enclosure 120 to an environment outsideof the enclosure 120 and/or the building via the purge exhaust outlet134 and corresponding purge exhaust outlet duct 138C, while fluidlyblocking the purge airflow 200 from traveling from the interior 122 ofthe enclosure 120 to the interior space of the building 10 via thelocked return inlet assembly 160 at the return inlet 130. Indeed, byforming the purge exhaust outlet 134 in an upstream portion 204 of theenclosure 120 relative to the supply fan 154, the leak management system102 enables the purge airflow 200 to be provided through the purgeexhaust outlet 134 by the supply fan 154 operating in reverse.Additionally, in some embodiments, the controller 170 instructs thesupply fan 154 to move the purge airflow 200 from the interior space ofthe building 10 until all or a portion of the air from the building 10is replaced. The controller 170 is capable of determining the portion orpercentage of the air that is removed, purged, or replaced from thebuilding 10 based on a predetermined volume of the building, as well asa volumetric flowrate of the purge airflow 200 and the amount of timefor which the volumetric flowrate has been produced. Thus, in someembodiments, the controller 170 instructs the supply fan 154 to purge atleast a threshold quantity of air from the interior space of thebuilding 10.

In certain embodiments, as the purge airflow 200 is moved out of theenclosure 120, one or more replacement airflows are drawn into theinterior space of the building 10. Generally, the replacement airflowdoes not include leaked refrigerant 116, such that the replacementairflows provided into the interior space of the building 10 dilute anyconcentration of the refrigerant 116 leaked into the enclosure 120. Thereplacement airflow may be provided into the interior space of thebuilding 10 via any suitable airflow path, such as one or more gapsbetween walls, windows, or other spaces or sealing defects of thebuilding 10. Additionally, in certain embodiments, the leak managementsystem 102 includes a purge inlet that fluidly couples the interiorspace of the building 10 to a fresh air source. In such embodiments, thefresh air source may be located on an opposed or different portion ofthe building 10 as the distal portion 142 of the purge exhaust outletduct 138C, such that fresh air is drawn into the building 10 to replacethe purge airflow 200. The purge inlet may thus include a purge inletassembly, such as a controller-actuated window, vent, or roof hatch thatis moveable to an open position upon instruction by the controller 170in the leak response mode. As such, embodiments having the purge exhaustinlet may enable faster replacement of the air within the building 10,while maintaining the structural security of the building 10. Indeed, anegative pressure caused by the operation of the supply fan 154 may drawthe replacement airflow from various air sources that are fluidlycoupled to the enclosure 120, such as gaps or imperfect seals betweenthe building 10 and the external environment 124.

Thus, when in the active detection mode, the leak management system 102operates the supply fan 154 in reverse to remove the leak of therefrigerant 116 from the interior space of the building 10, and to purgethe leaked refrigerant from the purge exhaust outlet 134 to the externalenvironment 124. By this technique, the leak management system 102reduces, eliminates, or prevents spreading of the leak of therefrigerant 116 throughout the building 10. Additionally, the controlsignals provided by the controller 170 in leak response mode are capableof operating the leak management system 102 to dilute, remove, ormitigate refrigerant 116 sourced from the detected refrigerant leakuntil the detected refrigerant leak is resolved. Moreover, one or moreof the above modifications to the HVAC system 100 may be performedsimultaneously, or within a time threshold relative to one another, tomore rapidly respond to the detected refrigerant leak. Additionally, insome embodiments, the controller 170 may prevent or block the HVACsystem 100 from operating until after the concentration of therefrigerant is again within the predefined concentration threshold, oruntil after the detected refrigerant leak is repaired. In someembodiments, the controller 170 determines the detected refrigerant leakis repaired based on user input received from a user device indicativeof a completed repair. As such, the embodiments of the HVAC system 100that include the disclosed leak management system 102 are able to purgethe leaked refrigerant from the interior space of the building 10.

In some embodiments, the controller 170 may employ a feedback loop todynamically adjust the modifications to the HVAC system 100 and leakmanagement system 102 in leak response mode. That is, the controller 170may implement a dynamic response strategy that monitors theconcentration of the refrigerant 116 after the refrigerant leak isdetected to evaluate an effectiveness of the modifications to the HVACsystem 100. Thus, the controller 170 further modifies and/or adjustsoperation of the HVAC system 100 and the leak management system 102based on the determined effectiveness of the corrective actions taken.For example, under certain conditions, after determining that theconcentration of the refrigerant 116 proximate the enclosure 120 remainsabove the predefined concentration threshold, the controller 170instructs the supply fan 154 to increase a fan speed of the supply fan154 that is operating in reverse. For example, the fan speed may beincreased by increasing a voltage or current applied to the supply fan154. Then, the controller 170 receives signals indicative of theconcentration of the refrigerant 116 from one or more of theconcentration sensors 190. In some embodiments, the signals are receivedcontinuously, at regular intervals, every minute, every 10 minutes, orthe like. Based on the received signals, the controller 170 continues todetermine the concentration of the refrigerant 116. If the controller170 determines that the concentration of the refrigerant 116 has droppedor is dropping below the predefined concentration threshold, thecontroller 170 may instruct the supply fan 154 to maintain the currentfan speed or return to a normal operating fan speed.

However, if the controller 170 determines that the concentration of therefrigerant 116 is not diminishing, such as remaining above thepredefined concentration threshold or continuing to increase after apredetermined amount of time, the controller 170 may instruct the supplyfan 154 to further increase the fan speed thereof, moving more air andleaked refrigerant 116 as the purge airflow 200 from the building 10,through the enclosure 120 and out through the purge exhaust outlet 134.The dynamic response strategy may be implemented across any range of fanspeeds that the supply fan 154 operating in reverse may produce. Thus,the controller 170 controls the leak management system 102 to bothdetect and mitigate detected refrigerant leaks from the HVAC system 100to block or prevent the refrigerant 116 from reaching the predefinedconcentration threshold within the interior space of the building 10.

In further embodiments, the leak management system 102 includes anadditional verification sensor disposed within the enclosure 120 orwithin any suitable duct 138 to detect whether the leak managementsystem 102 is purging the detected refrigerant leak from the building.For example, in certain embodiments, the verification sensor is aflowrate sensor capable of measuring a flowrate produced by the supplyfan 154 through the purge exhaust outlet 134 and/or the purge exhaustoutlet duct 138C. Thus, the flowrate sensor provides feedback to thecontroller 170 indicative of the flowrate produced by the supply fan154. The controller 170 compares the flowrate produced by the supply fan154 to a target flowrate set for the supply fan 154 to determine whetherthe actual flowrate is within a threshold of the target flowrate. If theactual flowrate is outside of the threshold, the controller 170 mayperform a suitable control action, such as providing control signalsthat generate and provide alerts indicative of the actual flow rate ofthe supply fan 154 being outside of the threshold from the targetflowrate, increasing other control actions, shutting down the leakmanagement system 102, or any other suitable control action. Moreover,any other suitable parameter may be monitored and controlled based oninput from other suitable verification sensors, such as a pressuresensor, a temperature sensor, etc.

Additionally, in certain embodiments, existing HVAC systems 100 may beretroactively fitted with the leak management systems 102 discussedherein. In such embodiments, the enclosure 120 may be modified byforming one or more new openings to include the purge exhaust outlet134. A purge exhaust outlet duct 138C may be coupled to the purgeexhaust outlet 134. Further, the return inlet assembly 160 and purgeexhaust outlet assembly 164 and the purge inlet assembly 222 may bedisposed respectively at the return inlet 130 and the purge exhaustoutlet 134. Thus, the leak management systems 102, or any other suitableembodiments of leak management systems discussed herein may be added toexisting enclosures of HVAC systems to enable refrigerant leak detectionand mitigation.

FIG. 8 is a front perspective view of an embodiment of the return inletassembly 160 of the leak management system 102. As illustrated, thereturn inlet assembly 160 is one of the airflow management assemblies158 disposed within or at the inlets and outlets of the enclosure 120.To fluidly isolate the interior 122 of the enclosure 120 from the returninlet duct 138A fluidly coupled to the return inlet 130, the returninlet assembly 160 includes the damper 180 rigidly coupled to the pivotmember 182. The damper 180 may be a flexible or semi-flexible panel thatis attached to, or integrally formed with, the pivot member 182 by anysuitable means. Additionally, the pivot member 182 is a cylindrical ortubular member having pivot pins 250 extending therefrom to enable thedamper 180 to pivot around a circumferential axis of the pivot pins 250in response to an airflow. As shown in the present embodiment of thereturn inlet assembly 160, the pivot pins 250 are disposed throughopenings 252 in walls 254 of the enclosure 120. However, in otherembodiments, the pivot pins 250 may alternatively be held incorresponding recesses, or may be replaced by other suitable componentsfor enabling pivoting relative to the enclosure 120.

Additionally, the leak management system 102 includes one or morelocking mechanisms 256 discussed above. For example, as seen in theembodiment of FIG. 8, two locking mechanisms 256 each include shafts 260that extend through corresponding openings 262 or lower openings in thewalls 254 of the enclosure 120. The locking mechanisms 256 are linearactuators that are electrically actuated via signals from the controller170. However, other suitable locking mechanisms, such as hydraulicallyactuated linear actuators may also be used in the techniques disclosedherein. The shafts 260 are extended within the return inlet duct 138Aadjacent or directly adjacent to the return inlet 130, and thus lock thedamper 180 in the closed position. In conditions in which the controller170 is not actuating the locking mechanisms 256, the shafts 260 areretracted at least partially within the corresponding openings 262, suchthat the damper 180 is free to rotate in response to an airflow pushingon an exterior surface of the damper 180 opposite of a presentlyvisible, interior surface 270 of the damper 180. Locking mechanisms 256may also be included within the leak management system 102 to enablecontrol of the purge exhaust outlet assembly 164 as well. In otherembodiments, other types of airflow management mechanisms and/or lockingmechanisms may be used, in accordance with the present disclosure.

For example, FIG. 9 is a front perspective view of an embodiment of areturn inlet assembly 300 of the leak management system 102. Asillustrated, the return inlet assembly 300 includes similar componentsto the return inlet assembly 160 of FIG. 8. For example, the returninlet assembly 300 also includes the pivot member 182 having the pivotpins 250 extending through the openings 252 in the walls 254 of theenclosure 120. However, the present embodiment of FIG. 9 also includes arigid damper 302 coupled to or integrally formed with the pivot member182. The illustrated rigid damper 302 is formed from a stiff sheet, suchas a sheet made of structurally supported rubber, from metal, etc.Additionally, a proximal pivot pin 304 of the pivot pins 250 is coupledto a drive mechanism, such as an illustrated motor assembly 310. Uponinstruction by the controller 170, the motor assembly 310 drives therigid damper 302 to rotate via applying torque to the proximal pivot pin304. In this manner, the motor assembly 310 may move the return inletassembly 300 to any suitable open, partially open, or closed position toenable the leak management system 102 to alternatively condition theinterior space of the building 10, or purge the air and leakedrefrigerant within the building 10 out through the purge exhaust outlet134. A motor assembly 310 may also be used to actively control theposition of the purge exhaust outlet assembly 164 as well. In certainembodiments, employing the motor assembly 310 in place of the lockingmechanisms 256 reduces a number of components, a number of openings orrecesses in the enclosure walls, and/or an installation time for theHVAC system 100.

FIG. 10 is a flow diagram illustrating an embodiment of a process 350for operating the leak management system 102 of FIG. 5. It is to beunderstood that the steps discussed herein are merely exemplary, andcertain steps may be omitted or performed in a different order that theorder discussed herein. The process 350 may be performed by thecontroller 170 via one or more processors, such as the processor 174 ofthe controller 170, an additional processor, or a combination thereof.First, as indicated in block 352, the illustrated process 350 includesthe controller 170 entering active detection mode. As discussed above,the controller 170 operates in active detection mode during bothON-cycle and OFF-cycle of the HVAC system 100. However, in someembodiments, the controller 170 may additionally switch to operate in anidle mode that does not actively monitor the concentration of therefrigerant 116 during ON-cycles of the HVAC system 100, upon userrequest, or during any other suitable times when detecting theconcentration of the refrigerant 116 is not performed.

Continuing along the illustrated process 350, the controller 170provides a first set of control signals to close the purge exhaustoutlet assembly 164, as indicated in block 354. As discussed above withrespect to FIG. 5, in active detection mode, the controller 170maintains the purge exhaust outlet assembly 164 in the closed position,such that the unconditioned airflow 144 may travel through the enclosure120 to be conditioned without the supply fan 154 drawing in outside airthrough the purge exhaust outlet 134. In certain embodiments, the purgeexhaust outlet assembly 164 remains in the closed position from startupor installation of the HVAC system 100 until a refrigerant leak isdetected, such that the first set of control signals are not provided.To enable the conditioning of the unconditioned airflow 144 duringON-cycle of the HVAC system 100, the controller 170 allows the returninlet assembly 160 to remain open. Then, the controller 170 receives asignal indicative of a concentration of the refrigerant 116 proximatethe enclosure 120, as indicated in block 356. The one or moreconcentration sensors 190 disposed proximate the enclosure 120 maytransmit the signal indicative of the concentration of the refrigerant116 to the controller 170. Indeed, the concentration sensors 190 maytransmit the signal continuously, at regular intervals, or afterdetecting a change in the concentration of the refrigerant 116 proximatethe enclosure 120, such as within the enclosure 120 and/or within theducts 138.

Additionally, the controller 170 determines the concentration of therefrigerant 116 proximate the enclosure 120, as indicated in block 358.As discussed above, the controller 170 determines or monitors theconcentration of the refrigerant 116 based on the signal from theconcentration sensors 190. In embodiments having multiple concentrationsensors 190, the controller 170 is capable of determining theconcentration of the refrigerant 116 proximate each concentration sensor190. The illustrated process 350 also includes the controller 170determining whether the concentration of the refrigerant 116 is greaterthan the predefined concentration threshold, as indicated in block 360.For example, the predefined concentration threshold may be a parameterstored within the memory 172 of the controller 170, as discussed above.In response to determining, as indicated in block 360, that theconcentration of the refrigerant 116 is less than the predefinedconcentration threshold, the controller 170 waits, as indicated in block362, a predefined amount of time before returning to block 354 tocontinue providing the first set of control signals to maintain thepurge exhaust outlet assembly 164 in the closed position. Then, thecontroller 170 may continue to enable the return inlet assembly 160 tomove between open and closed positions that correspond to the currentcycle of the HVAC system 100, and continue receiving, as indicated inblock 356, the one or more signals indicative of the concentration ofthe refrigerant 116. By waiting before continuing to determine theconcentration of the refrigerant 116, the process 350 extends a usablelife of the concentration sensors 190, as compared to embodiments inwhich the concentration sensors 190 are operating continuously.

In response to determining, as indicted in block 360, that theconcentration of the refrigerant 116 is greater than the predefinedconcentration threshold, the controller 170 enters leak response mode,as indicated in block 364. That is, the controller 170 generallyprovides control signals to operate the leak management system 102 inleak response mode to mitigate a detected refrigerant leak. Asillustrated by the present embodiment of the process 350, the controller170 operates in leak response mode by selectively actuating the airflowmanagement assemblies 158 to enable a refrigerant laden airflow to beremoved from the interior space of the building 10. More particularly,in leak response mode, the controller 170 provides, as indicated inblock 366, a second set of control signals to open the purge exhaustoutlet assembly 164, to close the return inlet assembly 160, and toactuate the supply fan 154 in reverse. In the present embodiment, thecontrol signals provided by the controller 170 instruct the purgeexhaust outlet assembly 164 to open by instructing the correspondinglocking mechanisms 256 to unlock the dampers 180, such that an airflowcan open the unlocked damper 180 at the purge exhaust outlet 134.Additionally, when the supply fan 154 is actuated in reverse, the supplyfan 154 moves a refrigerant-containing airflow out of the unlocked purgeexhaust outlet assembly 164 to purge the building 10 of the leakedrefrigerant 116. Additionally, a replacement airflow is drawn into thebuilding 10 and mixes with the air and/or leaked refrigerant within thebuilding 10, thus lowering the concentration of the refrigerant 116 inthe building 10.

To perform dynamic feedback control in leak response mode, after athreshold amount of time, the controller 170 determines theconcentration of refrigerant 116 again, as indicated in block 368. Then,the controller 170 determines whether the concentration of therefrigerant 116 is diminishing, as indicated in block 370. For example,the concentration of the refrigerant 116 may be diminishing when theconcentration of the refrigerant 116 is decreasing from the initialdetected concentration, decreasing below the predefined concentrationthreshold, and/or has a rate of change greater than a rate of changethreshold. In response to determining, as indicated in block 370, thatthe concentration of the refrigerant is diminishing, the controller 170continues to provide the second set of control signals to the airflowmanagement assemblies 158 and the supply fan 154 to purge the building10, as indicated in block 372. In response to determining that theconcentration of the refrigerant is not diminishing, the controller 170provides a third set of control signals to instruct the supply fan 154to increase a speed of the supply fan 154 operating in reverse, thusincreasing, as indicated in block 374, a rate at which the leakedrefrigerant is purged from the building 10.

Additionally, the control signals from the controller 170 in leakresponse mode may cause the components of the HVAC system 100 to performany suitable control actions, such as transmitting an alert indicativeof the concentration of the refrigerant 116 to a user or to a servicetechnician and/or ceasing operation of the HVAC system 100. In general,a concentration of the refrigerant 116 that exceeds the predefinedconcentration threshold is indicative of a leak of the refrigerant 116.Thus, in certain embodiments, the control signals from the controller170 instigate control actions which inform users or service techniciansof the leak of the refrigerant 116 and/or control actions that mitigatethe leak of the refrigerant.

Accordingly, the present disclosure is directed to a leak managementsystem for detecting and mitigating leaks of a refrigerant within abuilding having a HVAC system. The leak management system includes aplurality of airflow management assemblies capable of fluidly isolatingan interior of the enclosure from ducts fluidly coupled to theenclosure. The leak management system also includes one or moreconcentration sensors that transmit signals indicative of theconcentration of the refrigerant proximate the enclosure to acontroller. The controller monitors the concentration of the refrigerantin coordination with the operation of the HVAC system. In response todetermining that the concentration exceeds a predefined concentrationthreshold, the controller provides control signals to modify operationof the HVAC system and/or the leak management system. For example, thecontrol signals generally instruct the airflow management assemblies tofluidly couple an interior space of the building to a purge exhaustoutlet positioned upstream of a reversible supply fan. Then, the controlsignals activate the supply fan in reverse, thus purging the leakedrefrigerant from the interior space of the building out of the purgeexhaust outlet. The controller may also cause a device to transmit analert indicative of the concentration of the refrigerant and/or stopoperation of the HVAC system until the leak of refrigerant is resolved.In this manner, the leak management system enables the detection andmitigation of refrigerant leaks substantially before the refrigerant mayreach the predefined concentration threshold.

While only certain features and embodiments of the present disclosurehave been illustrated and described, many modifications and changes mayoccur to those skilled in the art, such as variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters such as temperatures, pressures, etc., mountingarrangements, use of materials, orientations, etc., without materiallydeparting from the novel teachings and advantages of the subject matterrecited in the claims. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. It is, therefore, to be understood that the appended claimsare intended to cover all such modifications and changes as fall withinthe true spirit of the disclosure. Furthermore, in an effort to providea concise description of the embodiments, all features of an actualimplementation may not have been described, including those unrelated tothe presently contemplated best mode of carrying out the disclosure, orthose unrelated to enabling the claimed features. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerous implementationspecific decisions may be made. Such a development effort might becomplex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure, without undueexperimentation.

The invention claimed is:
 1. A refrigerant leak management system for aheating, ventilation, and/or air conditioning (HVAC) system, wherein therefrigerant leak management system comprises: a controllercommunicatively coupled to a sensor and a supply fan that is disposedwithin an air handling enclosure of the HVAC system, wherein thecontroller is configured to: receive, from the sensor, a sensor signalindicative of a refrigerant leak; and in response to receiving thesensor signal, activate the supply fan to direct a flow ofrefrigerant-containing air from an interior space of a building and intothe air handling enclosure via a supply outlet of the air handlingenclosure.
 2. The refrigerant leak management system of claim 1, whereinthe sensor signal indicative of the refrigerant leak comprises aconcentration sensor signal indicative of air having a refrigerantconcentration that is greater than a predefined concentration threshold,and wherein, in response to receiving the concentration sensor signal,the controller is configured to switch operation of the refrigerant leakmanagement system from an active detection mode, which enables ON-cycleoperation of the HVAC system, to a leak response mode that disables theON-cycle operation.
 3. The refrigerant leak management system of claim2, wherein the controller is configured to switch operation of therefrigerant leak management system from the leak response mode to theactive detection mode in response to: receiving user input from an inputdevice; receiving, from the sensor or an additional sensor, anadditional sensor signal indicative of the air having the refrigerantconcentration that is less than the predefined concentration threshold;or both.
 4. The refrigerant leak management system of claim 1, whereinthe controller is communicatively coupled to a return inlet assemblythat is coupled to a return inlet of the air handling enclosure, andwherein, in response to receiving the sensor signal, the controller isconfigured to instruct the return inlet assembly to seal the returninlet to block the flow of the refrigerant-containing air from travelingthrough the return inlet.
 5. The refrigerant leak management system ofclaim 4, wherein the controller is configured to instruct the returninlet assembly to seal the return inlet during OFF-cycle operation ofthe HVAC system.
 6. The refrigerant leak management system of claim 4,wherein the return inlet assembly comprises a locking mechanismconfigured to selectively retain a barometric damper in a closedposition that seals the return inlet, and wherein the controller isconfigured to instruct the return inlet assembly to seal the returninlet by instructing the locking mechanism to retain the barometricdamper in the closed position.
 7. The refrigerant leak management systemof claim 4, wherein the return inlet assembly comprises a motorizeddamper that is movable between an open position that opens the returninlet and a closed position that seals the return inlet, and wherein thecontroller is configured to instruct the return inlet assembly to sealthe return inlet by instructing the motorized damper to move to orremain in the closed position.
 8. The refrigerant leak management systemof claim 1, wherein the controller is communicatively coupled to a purgeoutlet assembly that is coupled to a purge outlet of the air handlingenclosure, and wherein, in response to receiving the sensor signal, thecontroller is configured to instruct the purge outlet assembly to openthe purge outlet to direct the flow of the refrigerant-containing airout of the purge outlet.
 9. The refrigerant leak management system ofclaim 8, wherein the purge outlet assembly comprises: a motorized dampercoupled to the purge outlet; or a locking mechanism configured toselectively retain a barometric damper coupled to the purge outlet. 10.The refrigerant leak management system of claim 1, wherein the supplyfan is configured to be activated in a reverse direction to direct theflow of the refrigerant-containing air from the interior space of thebuilding and into the air handling enclosure via the supply outlet, andfurther comprising a passive purge outlet assembly configured to seal apurge outlet of the air handling enclosure in response to the supply fanbeing activated in a forward direction or deactivated, and whereinactivating the supply fan in the reverse direction causes the passivepurge outlet assembly to open by directing the flow of therefrigerant-containing air against the passive purge outlet assembly.11. The refrigerant leak management system of claim 1, wherein thecontroller is configured to activate the supply fan to discharge a flowof conditioned air from the air handling enclosure and into the interiorspace of the building via the supply outlet in response to receiving arequest for conditioning from a thermostat when the sensor signal is notreceived.
 12. The refrigerant leak management system of claim 2, whereinthe controller is configured to: receive, from the sensor, an additionalsensor signal indicative of the air having the refrigerant concentrationthat is greater than the predefined concentration threshold after athreshold amount of time; and increase a fan speed of the supply fan inresponse to the additional sensor signal.
 13. A tangible,non-transitory, machine-readable medium, comprising machine-readableinstructions that are executable by one or more processors of acontroller of a heating, ventilation, and air/or conditioning (HVAC)system, wherein the instructions comprise instructions to: receive asensor signal indicative of a refrigerant concentration of air from asensor of the HVAC system; determine that the refrigerant concentrationis indicative of a refrigerant leak; and in response to determining thatthe refrigerant concentration is indicative of the refrigerant leak,activate a supply fan of the HVAC system in a reverse direction todirect a flow of refrigerant-containing air from an interior space of abuilding into an air handling enclosure of the HVAC system.
 14. Thetangible, non-transitory, machine-readable medium of claim 13, whereinthe instructions comprise instructions to activate a return inletassembly to seal a return inlet of the air handling enclosure inresponse to determining that the refrigerant concentration is indicativeof the refrigerant leak.
 15. The tangible, non-transitory,machine-readable medium of claim 14, wherein the return inlet assemblycomprises a motorized damper or a locking mechanism configured toselectively retain a barometric damper.
 16. The tangible,non-transitory, machine-readable medium of claim 14, wherein theinstructions comprise instructions to activate a purge outlet assemblyto open a purge outlet of the air handling enclosure to direct the flowof the refrigerant-containing air out of the purge outlet in response todetermining that the refrigerant concentration is indicative of therefrigerant leak.
 17. The tangible, non-transitory, machine-readablemedium of claim 16, wherein the instructions comprise instructions toactivate the supply fan in the reverse direction, activate the returninlet assembly to seal the return inlet, and activate the purge outletassembly to open the purge outlet at substantially the same time. 18.The tangible, non-transitory, machine-readable medium of claim 13,wherein the instructions comprise instructions to determine that therefrigerant concentration is indicative of the refrigerant leak inresponse to determining that the refrigerant concentration is above alower detection limit of the sensor.
 19. The tangible, non-transitory,machine-readable medium of claim 13, wherein the instructions compriseinstructions to: receive an additional sensor signal indicative of anadditional refrigerant concentration from an additional sensor of theHVAC system; and determine a position of the refrigerant leak based onthe sensor signal and the additional sensor signal.
 20. The tangible,non-transitory, machine-readable medium of claim 13, wherein theinstructions comprise instructions to: receive an additional sensorsignal indicative of the refrigerant concentration from the sensor or anadditional sensor after a threshold amount of time; determine that therefrigerant concentration remains indicative of the refrigerant leak;and increase a fan speed of the supply fan in the reverse direction inresponse to determining that the refrigerant concentration remainsindicative of the refrigerant leak.
 21. An air handling system of aheating, ventilation, and/or air conditioning (HVAC) system for abuilding, wherein the air handling system comprises: a sensor disposedwithin an enclosure of the air handling system; a supply fan disposedwithin the enclosure; and a controller communicatively coupled to thesensor and the supply fan, wherein the controller is configured to:receive a sensor signal indicative of air having a refrigerantconcentration that is greater than a predefined concentration thresholdfrom the sensor; and in response to receiving the sensor signal,activate the supply fan in a reverse direction to draw a flow ofrefrigerant-containing air from an interior space of the building intothe enclosure.
 22. The air handling system of claim 21, wherein, inresponse to receiving the sensor signal, the controller is configured toinitiate a leak response mode that disables activation of a compressorof the HVAC system and disables activation of the supply fan in aforward direction.
 23. The air handling system of claim 21, wherein thesensor is disposed proximate an evaporator coil of the HVAC system andproximate a bottom surface of the enclosure.
 24. The air handling systemof claim 21, wherein the sensor is disposed downstream of the supply fanrelative to a flow path of the flow of the refrigerant-containing airinto the enclosure.
 25. The air handling system of claim 21, comprisinga return inlet assembly that is coupled to a return inlet of theenclosure, wherein, in response to receiving the sensor signal, thecontroller is configured to instruct the return inlet assembly to sealthe return inlet to block the flow of the refrigerant-containing airfrom traveling through the return inlet.
 26. The air handling system ofclaim 21, comprising a purge outlet assembly that is coupled to a purgeoutlet of the enclosure, wherein the purge outlet assembly is configuredto enable the supply fan to direct the flow of therefrigerant-containing air out of the purge outlet when the supply fanis activated in the reverse direction.
 27. The air handling system ofclaim 26, wherein the controller is configured to instruct the purgeoutlet assembly to open the purge outlet in response to receiving thesensor signal.